To date, gate valves of various types of mechanisms have been proposed for use in maintaining the vacuum of a vacuum chamber of such as semiconductor manufacturing equipment.
For example, Patent literature 1 describes a gate valve. The gate valve described there has a housing having a gas passage. The housing accommodates a round-shaped valve plate (valve body); and to the housing, a driving device is attached. The driving device has a shaft that connects to the valve plate and an actuator that drives the shaft. The driving device linearly moves the valve plate to open or close the gas passage. The gate valve in that disclosure is, for instance, installed between a vacuum chamber and a vacuum pump in a semiconductor manufacturing equipment and opens or closes the gas passage between the vacuum chamber and the vacuum pump. This means that the gate valve described in Patent literature 1 electrically opens or closes. The literature further mentions that the actuator may be constituted of an electric motor, a ball screw that is rotated by the electric motor, and a ball screw nut that engages with the ball screw.
Further, Patent literature 2 describes another gate valve. The valve described there is comprised of a valve body (housing); a gate assembly accommodated in the valve body, wherein the gate assembly opens and closes openings formed on the valve body confronting each other; a first cylinder that is a first driving device for open and close movements of the gate assembly; and a second cylinder that is a second driving device for a sealing movement of the gate assembly, wherein the valve body has an opening. This gate valve is controlled by a control device of a system so that the open and close movements and the sealing movement of the gate assembly will be taken place independently each other by the first cylinder and the second cylinder. Each of these cylinders is designed to be fed with compressed air from an air source and thereby its cylinder rod is driven. The literature further mentions that a seal ring (a sealing material) such as an O-ring is provided on the gate assembly.
In each of the gate valves described in the patent literatures cited above, the valve body is arranged confronting the valve seat in the valve body. In this configuration, the driving device drives the valve body toward the valve seat and the valve body presses the sealing material against the valve seat to make the sealing material squeezed; and thereby the airtightness between the inside and outside of the valve body and the valve seat is secured. Hereunder, securing an airtight state is referred to simply as “sealing”.